Loop Diuretics - Cardiovascular Poison

Loop Diuretics

These agents are inhibitors of sodium-potassium-chloride symport in the ascending limb of the loop of Henle, and are highly efficient diuretics. Therefore they are also referred to as high-ceiling diuretics. Examples include furosemide,bumetanide, azosemide, piretanide, tripamide, muzolimine, torasemide, etozolin, ozolinone, and ethacrynic acid.

Uses

Treatment of

·              Acute pulmonary oedema

·              Chronic congestive heart failure

·              Hypertension

·              Nephrotic syndrome

·              Cirrhosis of liver

·              Poisoning (to increase renal elimination by forced diuresis).

Drug Interactions

·      Increased ototoxicity with aminoglycosides

·      Increased incidence of arrhythmias with digitalis

·      Increased incidence of hyperglycaemia with sulfonylureas

·              Blunted diuretic response with NSAIDs

·      Synergism with thiazides.

Adverse Effects and Toxic Features

·      Overdose causes hyponatraemia (with or without extacel-lular fluid volume depletion), hypotension, and circula-tory collapse. In addition, there may be hypochloraemic alkalosis, hypokalaemia, and hypomagnesaemia (with cardiac arrhythmias), and hypocalcaemia (with tetanic manifestations). 

·      Ventricular arrhythmias and syncope have been reported following high-dose intravenous therapy with furo-semide.

·      GI bleeding may occur during therapy with ethacrynic acid and furosemide, particularly in patients with renal failure.

·             Other effects include hyperuricaemia, hyperglycaemia, and ototoxicity manifesting as tinnitus, vertigo, and deafness.

Treatment

Treatment comprises supportive and symptomatic measures. Diuretic blood levels are not clinically useful. Monitor fluid and electrolyte balance carefully and provide replacement therapy as needed.